CLARKE: ECOLOGY OF LANTERNFISHES 



those over 45 mm below 125 m. D. rolflyoUiii 

 was caught in roughly similar numbers at all 

 seasons; however, trends in size composition 

 were evident from the pooled data. In July 



1970, September 1970 and 1971, and June 



1971, 50% or more of the catches were <20 mm. 

 In December 1970, almost all were between 

 20 and 40 mm, and in March 1971, both CT and 

 IK catches were mostly between 45 and 55 

 mm. Individuals over 55 mm were present in 

 low but consistent numbers all year round and 

 may be more than 1 year old. 



Dictphns elucens 



D. elucens showed definite changes in size 

 composition with depth at night. Size-frequency 

 curves from the CT series in March 1971 

 differed significantly. There were two size 

 groups present at that time, 32-47 mm and 

 49-63 mm. The smaller size group made up 

 80% , 73% , and 20% of the catches in tows at 50, 

 75, and 100 m, respectively. The number of 

 smaller fish was roughly equal in the two 

 shallower tows and those of larger fish compar- 

 able in the two deeper ones. In September 1971, 

 full moon, 98 individuals 7-11 mm long were 

 caught at 20 m, and 12 of 13-17 mm at 50 m. 

 Few of these sizes were taken in deeper water 

 where some larger individuals were caught. No 

 trends could be recognized in the daytime 

 samples. 



The pooled IK data indicated that D. elucens 

 spawns in late summer and reaches maturity 

 in about 1 year. In June 1971 and July 1970, 

 most individuals were over 40 mm. In Septem- 

 ber 1970 there were two distinct size classes, 

 10-13 mm and over 46 mm with practically 

 none in between. In September 1971, new moon, 

 there was a broad group 10-29 mm and a few 

 over 50 mm. In the full moon series, there was 

 a distinct group at 7-11 mm, a smaller group at 

 12-18 mm, and practically none larger. In 

 December 1970, 70% were 23-41 mm, and in 

 March 1971, the two size groups mentioned 

 above were present in both IK and CT data. 



Diciphns sp. A and B 



D. sp. A and B are superficially similar to 



each other and resemble most closely D. mollis 

 from the Atlantic, but both appear to be distinct 

 species. All but the smallest specimens can be 

 readily distinguished. Species A has a rounded 

 opercular margin, and the eyes of Formalin- 

 preserved specimens are distinctly green. In 

 species B, the upper opercular margin is dis- 

 tinctly angular or hooked, and the eyes are 

 yellow-white. The counts for fully developed 

 gill rakers were usually 4 + 1-1-10 for species 

 A and 5+1 + 10-12 for species B. Species B 

 matures at and reaches a much larger size 

 than species A. 



Species A was taken in abundance (>10/tow) 

 only 13 times, and size-frequency curves could 

 be compared only for samples from the July 

 1970 and March 1971 CT series. These both 

 indicated significant differences with the smaller 

 fish occurring in shallower water. The one 

 daytime comparison possible, in September 

 1970, showed no difference between tows at 500 

 and 575 m. There was no evidence that any 

 sizes did not migrate regularly. 



There were no obvious differences in abun- 

 dance and size frequency between day and night 

 tows. Two CT tows in March 1971 caught 

 species A similar in size composition to the 

 two positive IK tows, but the CT catches were 

 highest at 50 m and substantial at 75 m whereas 

 the IK indicated a peak at 25 m and only a few 

 at 50 m. At new moon, the depth of highest 

 catch was at 45 m and at full moon was at 

 75 m. The catch at new moon was about 5 x 

 that at full moon, indicating greater avoidance 

 as well as depression during full moon. 



Abundance was distinctly higher during 

 July 1970 and September 1970 and 1971 with 

 the largest proportion of small fish at these 

 times. Abundance was distinctly lowest in 

 June 1971 and almost all were adults. These 

 data suggest that species A spawns in the 

 summer and reaches maturity in about 1 year. 

 However, the condition of the ovaries did not 

 indicate a restricted spawning season; 89-100% 

 of the mature females wei'e ripe at all seasons 

 (Table 2). 



Only the juveniles (<15 mm) of species B 

 occurred above 100 m. Abundance was highest 

 in June 1971 and most of the catch was juveniles 



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